QVidium QVAVQ Series v4 - Manual (Page 21)

User’s Manual v.4 QVidium ® QVARQ QoS Proxy Server™
21 of 24 - Copyright 2010 QVidium
®
Technologies, Inc.
5.2 Appendix B: Receive Proxy Configuration Parameters
This section explains the parameters related to the setup and operation of the receive
proxy, the error correction algorithms, and network transport configuration.
Network Parameters
The fields below relate to Ethernet/IP video transport settings.
IP Transport: This selects the type of video IP packet decapsulation and error correction
expected by the codec in receiving a Video/IP stream.
• ARQ uses QVidium’s patented error correction mechanism for lost packet
recovery. ARQ encapsulates the video stream as a standard MPEG-2 Transport
Stream as the payload of UDP packets with an RTP packet header as per
RFC2733. It relies upon an upstream channel on UDP port 7020.
• RTP disables all error correction mechanisms, but still allows measuring packet
loss.
• UDP is similar to the RTP transport above, but expects raw UDP packets without
an RTP header. It expects to receive the MPEG-2 transport stream directly from
the UDP payload. Use this setting for interoperability with some Set-Top Boxes.
Multicast Address: This specifies the IP multicast address, if any, to listen to for the
Video/IP stream. For receiving a unicast video/IP stream, leave this field blank.
UDP Port: This specifies which UDP port number (P), base 10, to listen on for the
Video/IP stream.
Jitter: Packets in incoming IP packet streams may lose their ordering or suffer variable
delays during transport through an IP network. The proxy receiver buffers all incoming
video/IP packets in a buffer and reorders RTP encapsulated packets by RTP sequence
number. This parameter specifies the size of this incoming packet buffer in milliseconds of
delay. Specify 0 here to disable this additional buffering when latency needs to be
minimize.
ARQ Parameters
The parameters below ONLY pertain to QVidium ARQ error correction. They will be
ignored unless ARQ is selected for IP Transport.
Target Latency: QVidium’s ARQ error correction operates through the addition of a
small additional buffering delay to provide enough time to request and receive
replacement for each lost packet. Target Latency gives the ARQ mechanism a target value
for determining the necessary ARQ delay. The ARQ divides the Target Latency, specified
in milliseconds, by the round-trip time to the video encoding source to determine the
number of request attempts. Unless Robust Mode is enabled, it sets a minimum ARQ